The presently disclosed subject matter relates to a mask which is attached to the face of a subject so as to introduce the expired gas of the subject to an expired gas concentration detection sensor.
As an example of such a mask, Patent Document 1 discloses an oxygen mask which includes a wall section, an expired gas introduction section, and a communication section. The wall section defines an internal space of the mask so as to cover at least a portion of a nose and a mouth of the subject. The expired gas introduction section is disposed in the internal space so as to introduce the expired gas of the subject. The communication section defines a communication channel which is supported by the wall section and through which the expired gas of the subject is introduced into an expired gas concentration detection sensor.
[Patent Document 1] JP-A-2011-115543
The shape of the faces to which such a mask is attached is different for each subject. Particularly, the shape of a nose to which the expired gas introduction section is in close proximity is different for each subject. Owing to this difference in facial shapes, the expired gas of the subject is often not surely introduced into the expired gas concentration detection sensor.
Accordingly, the presently disclosed subject matter aims as providing the technique to make sure the introduction of the expired gas of a subject to an expired gas concentration detection sensor regardless of the subjects' facial shapes.